U.S. patent application number 14/845766 was filed with the patent office on 2015-12-31 for process for degassing condensed sulfur from a claus sulfur recovery system.
This patent application is currently assigned to PHILLIPS 66 COMPANY. The applicant listed for this patent is PHILLIPS 66 COMPANY. Invention is credited to Alfred E. Keller.
Application Number | 20150376008 14/845766 |
Document ID | / |
Family ID | 54929739 |
Filed Date | 2015-12-31 |
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United States Patent
Application |
20150376008 |
Kind Code |
A1 |
Keller; Alfred E. |
December 31, 2015 |
PROCESS FOR DEGASSING CONDENSED SULFUR FROM A CLAUS SULFUR RECOVERY
SYSTEM
Abstract
A process of producing degassed liquid sulfur using agitation
gas to agitate the liquid sulfur being degassed while in contact
with a degassing catalyst. Process gas may be blended with the
agitation gas wherein the process gas contains H.sub.2S to
accomplish substantial degassing rendering the liquid sulfur much
safer in storage and transportation.
Inventors: |
Keller; Alfred E.; (Katy,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PHILLIPS 66 COMPANY |
Houston |
TX |
US |
|
|
Assignee: |
PHILLIPS 66 COMPANY
Houston
TX
|
Family ID: |
54929739 |
Appl. No.: |
14/845766 |
Filed: |
September 4, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14304306 |
Jun 13, 2014 |
9138675 |
|
|
14845766 |
|
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Current U.S.
Class: |
423/574.1 ;
423/573.1 |
Current CPC
Class: |
B01D 5/0012 20130101;
B01D 5/0051 20130101; B01D 5/0093 20130101; C01B 17/0232 20130101;
C01B 17/0447 20130101; B01D 19/0052 20130101 |
International
Class: |
C01B 17/05 20060101
C01B017/05 |
Claims
1. A process for producing liquid sulfur that is degassed of
H.sub.2S, wherein the process comprises: a) providing a sulfur
degassing catalyst and liquid sulfur into a vessel wherein the
sulfur degassing catalyst and liquid sulfur define a contact zone;
b) directing condensed products from a Claus plant into the contact
zone of the vessel wherein the condensed products include elemental
sulfur, dissolved H.sub.2S and H.sub.2S.sub.x where x.gtoreq.2; c)
catalyzing the conversion of H.sub.2S.sub.x on the surface of the
sulfur degassing catalyst to form H.sub.2S and elemental sulfur; d)
directing agitation gas at an elevated pressure into the contact
zone of the vessel to agitate the sulfur degassing catalyst and
liquid sulfur and carry H.sub.2S that has formed on the surface of
the sulfur degassing catalyst away from the sulfur degassing
catalyst; e) blending process gas drawn from an intermediate step
of the Claus plant into the agitation gas prior to the agitation
gas being directed into the contact zone; f) exhausting the
agitation gas along with H.sub.2S from the contact zone to the
Claus plant for further processing in the Claus plant; and g)
extracting liquid sulfur that is degassed of H.sub.2S from the
contact zone.
2. The process according to claim 1, wherein the step of providing
a sulfur degassing catalyst comprises providing a plurality of high
surface area alumina particles constrained to prevent being removed
or carried away from the contact zone.
3. The process according to claim 2, wherein the step of providing
a sulfur degassing catalyst further comprises providing a plurality
of high surface area alumina particles impregnated with iron
oxide.
4. The process according to claim 1, wherein the step of providing
a sulfur degassing catalyst comprises providing one or more low
surface area alumina porous ceramic foam supports coated with high
surface alumina particles.
5. The process according to claim 4, wherein the step of providing
a sulfur degassing catalyst further comprises providing one or more
low surface area alumina porous ceramic foam supports coated with
high surface alumina particles that is impregnated with iron
oxide.
6. The process according to claim 1 wherein the process gas
includes H.sub.2S.
7. The process according to claim 1 wherein the agitation gas is
nitrogen.
8. The process according to claim 1 wherein the agitation gas is
carbon dioxide.
9. The process according to claim 1 where the agitation gas is
inert.
10. The process according to claim 1, the Claus process includes at
least three condensers, but only the liquid sulfur from the first
two condensers are subject to degassing in the contact zone.
11. The process according to claim 1 further including converting
H.sub.2S to elemental sulfur by reacting on the surface of the
catalyst with SO.sub.2 in the process gas by the following
reaction: 2H.sub.2S+SO.sub.23/x S.sub.x+2H.sub.2O.
12. A process for producing liquid sulfur that is degassed of
H.sub.2S, wherein the process comprises: a) providing a Claus plant
for desulfurizing H.sub.2S containing gases, wherein the Claus
plant includes a number of components such as a burner for
converting some H.sub.2S to SO.sub.2 along with elevated pressure
process gas, a reaction furnace for converting at least some
H.sub.2S and SO.sub.2 to elemental sulfur, a first condenser for
condensing the sulfur from the process gas exiting the reaction
furnace, at least one additional catalytic reactor for converting a
portion of the H.sub.2S in the process gas from the first condenser
to elemental sulfur, a second condenser for condensing the sulfur
in the gases exiting the one additional catalytic reactor; b)
providing a sulfur degassing catalyst and liquid sulfur into a
vessel wherein the sulfur degassing catalyst and liquid sulfur
define a contact zone; c) directing condensed products from at
least one condenser of the Claus plant to the vessel, wherein the
condensed products include elemental sulfur, dissolved H.sub.2S and
H.sub.2S.sub.x where x.gtoreq.2; d) catalyzing the conversion of
H.sub.2S.sub.x on the surface of the sulfur degassing catalyst in
the contact zone to form H.sub.2S and elemental sulfur; e)
directing agitation gas into the contact zone of the vessel to
agitate the sulfur degassing catalyst and liquid sulfur and carry
H.sub.2S that has formed on the surface of the sulfur degassing
catalyst away from the sulfur degassing catalyst; f) blending
process gas drawn from an intermediate step of the Claus plant into
the agitation gas prior to the agitation gas being directed into
the contact zone; g) exhausting the agitation gas along with
H.sub.2S from the contact zone back to the Claus plant for further
processing in the Claus plant; and h) extracting liquid sulfur that
is degassed of H.sub.2S from the contact zone.
13. The process according to claim 12, wherein the step of
providing a sulfur degassing catalyst comprises providing a
plurality of high surface area alumina particles constrained to
prevent being removed or carried away from the contact zone.
14. The process according to claim 13, wherein the step of
providing a sulfur degassing catalyst further comprises providing a
plurality of high surface area alumina particles impregnated with
iron oxide.
15. The process according to claim 12, wherein the step of
providing a sulfur degassing catalyst comprises providing one or
more low surface area alumina porous ceramic foam supports coated
with high surface alumina particles.
16. The process according to claim 15, wherein the step of
providing a sulfur degassing catalyst further comprises providing
one or more low surface area alumina porous ceramic foam supports
coated with high surface alumina particles that is impregnated with
iron oxide.
17. The process according to claim 12 where in the process gas
includes H.sub.2S.
18. The process according to claim 12 wherein the agitation gas is
nitrogen.
19. The process according to claim 12 wherein the agitation gas is
carbon dioxide.
20. The process according to claim 12 where the agitation gas is
inert.
21. The process according to claim 12, the Claus process includes
at least three condensers, but only the liquid sulfur from the
first two condensers are subjected to degassing in the contact
zone.
22. The process according to claim 12 further including converting
H.sub.2S to elemental sulfur by reacting on the surface of the
catalyst with SO.sub.2 in the process gas by the following
reaction: 2H.sub.2S+SO.sub.23/x S.sub.x+2H.sub.2O.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional continuation-in-part
application of U.S. Ser. No. 14/304,306, filed Jun. 13, 2014,
entitled PROCESS FOR DEGASSING CONDENSED SULFUR FROM A CLAUS SULFUR
RECOVERY SYSTEM", and a claim is made under 35 USC .sctn.119(e) to
the parent application and additionally to the five applications to
which the parent application claimed benefit, which includes U.S.
Provisional Application Ser. No. 61/837,927 filed Jun. 21, 2013,
entitled "APPARATUS FOR IN-SITU PRODUCTION OF LOW DISSOLVED
HYDROGEN SULPHIDE, DEGASSED, SULFUR FROM CLAUS SULFUR RECOVERY,"
and to U.S. Provisional Application Ser. No. 61/837,944 filed Jun.
21, 2013, entitled "APPARATUS FOR IN-SITU PRODUCTION OF LOW
DISSOLVED HYDROGEN SULPHIDE, DEGASSED, SULFUR FROM CLAUS SULFUR
RECOVERY," and to U.S. Provisional Application Ser. No. 61/837,950
filed Jun. 21, 2013, entitled "PROCESS FOR IN-SITU PRODUCTION OF
LOW DISSOLVED HYDROGEN SULPHIDE, DEGASSED, SULFUR FROM CLAUS SULFUR
RECOVERY," and to U.S. Provisional Application Ser. No. 61/837,958
filed Jun. 21, 2013, entitled "PROCESS FOR IN-SITU PRODUCTION OF
LOW DISSOLVED HYDROGEN SULPHIDE, DEGASSED, SULFUR FROM CLAUS SULFUR
RECOVERY," and to U.S. Provisional Application Ser. No. 62/010,766
filed Jun. 11, 2014, entitled "PROCESS FOR DEGASSING CONDENSED
SULFUR FROM A CLAUS SULFUR RECOVERY SYSTEM", all six of which are
incorporated herein by reference in their entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] None.
FIELD OF THE INVENTION
[0003] This invention relates to the recovery of degassed sulfur
from a Claus sulfur recovery plant and especially to substantially
reducing the H.sub.2S content of liquid sulfur for the safe storage
and transportation of liquid sulfur.
BACKGROUND OF THE INVENTION
[0004] The Claus process is a gas desulfurizing process for
recovering elemental sulfur from gaseous hydrogen sulfide. It was
first developed in the 1880's and has become an industry standard
for refineries, chemical plants and natural gas processing plants.
As petroleum and natural gas is tending to contain ever increasing
amounts of sulfur compounds while fuel regulations are tending to
mandate less allowable sulfur in fuel, Claus processes become
increasingly important
[0005] A Claus plant, which is a multi-step process within a larger
industrial plant is arranged to recover sulfur from gaseous
hydrogen sulfide. Typically, elemental sulfur is produced by a
thermal step and several catalytic steps. Elemental sulfur is
separated from the Claus plant as a liquid at one or more
condensers.
[0006] While current sulfur condensers have proven satisfactory for
condensing sulfur, there is a need for improvement in the quality
of the sulfur condensed. The problem is that the condensed sulfur
includes dissolved H.sub.2S. Over an extended time, the H.sub.2S
will eventually disassociate from the liquid sulfur and accumulate
as a toxic and flammable gas in vapor spaces at the top of the
storage or transport vessels. Since an unsafe condition is possible
until the sulfur is fully degassed of dissolved H.sub.2S,
precautionary steps are required prior to opening a sulfur vessel
and while transferring liquid sulfur from one vessel to
another.
[0007] It has been found that it is the nature of a liquid sulfur
produced in a sulfur condenser process that reactant hydrogen
sulfide (H.sub.2S) is incorporated into the sulfur as simple
dissolved H.sub.2S and also as chemically bound with sulfur in the
form what is sometimes called a sulfane or polysulfane. Sulfane is
H.sub.2S.sub.x, (with x>1). H.sub.2S.sub.x will convert back to
H.sub.25 and elemental sulfur in time through an equilibrium
reaction which may be accelerated with a catalyst. This is a known
problem and most efforts to remove H.sub.2S from the elemental
sulfur include bubbling various gases such as air and preferably
inert gases such as nitrogen and carbon dioxide through the liquid
sulfur while in a catalyst bed. This degassing process, while
necessary, takes time and adds to the expense of capturing sulfur
from refineries, gas plants and chemical plants that deal with
sulfur.
[0008] Thorough degassing is imperative as capturing and disposing
of H.sub.25 that is emanating from liquid sulfur storage is another
issue. If the elemental sulfur is not adequately degassed, H.sub.2S
emanating from liquid sulfur storage may become a fugitive emission
in an area that is closely monitored for environmental compliance.
In some instances, up to half of the reported emissions from a
Claus sulfur recovery plant and Claus Tail Gas Cleanup unit can
come from H.sub.2S emanating from liquid sulfur in storage. Without
degassing operations or adequate capture and disposal technology,
these additional emissions may limit the sulfur processing
capability of the Claus/TGU (Tail Gas Unit) unit.
[0009] Technology is needed to reduce costs and overcome and
resolve these problems without creating new disadvantages.
BRIEF SUMMARY OF THE DISCLOSURE
[0010] The invention more particularly relates to a process for
producing liquid sulfur that is degassed of H.sub.2S. The process
includes a sulfur degassing catalyst providing a sulfur degassing
catalyst and liquid sulfur into a vessel wherein the sulfur
degassing catalyst and liquid sulfur define a contact zone and
condensed products are directed to the vessel from a Claus plant
into the contact zone of the vessel. These condensed products
include elemental sulfur, dissolved H.sub.2S and H.sub.2S.sub.x
where x>2. The conversion of H.sub.2S.sub.x is catalyzed on the
surface of the sulfur degassing catalyst to form H.sub.2S and
elemental sulfur and agitation gas is directed at an elevated
pressure into the contact zone of the vessel to agitate the sulfur
degassing catalyst and liquid sulfur. Process gas drawn from an
intermediate step of the Claus plant is blended into the agitation
gas prior to the agitation gas being directed into the contact
zone. The agitation gas also carries H.sub.2S that has formed on
the surface of the sulfur degassing catalyst away from the sulfur
degassing catalyst. The agitation gas along with H.sub.2S from the
contact zone are exhausted for further processing in the Claus
plant and liquid sulfur that is degassed of H.sub.2S is extracted
from the contact zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete understanding of the present invention and
benefits thereof may be acquired by referring to the follow
description taken in conjunction with the accompanying drawings in
which:
[0012] FIG. 1 is a flow diagram showing a basic and conventional
Claus sulfur recovery system;
[0013] FIG. 2 is a flow diagram showing liquid sulfur being
degassed of H.sub.2S;
[0014] FIG. 3 is a flow diagram of the vessel connected to the
Claus process;
[0015] FIG. 4 is a flow diagram of an alternative embodiment
showing the liquid sulfur being degassed of H.sub.2S; and
[0016] FIG. 5 is a flow diagram on another alternative embodiment
showing the inert gas pumping process gas into the degasser using
an eductor.
DETAILED DESCRIPTION
[0017] Turning now to the detailed description of the preferred
arrangement or arrangements of the present invention, it should be
understood that the inventive features and concepts may be
manifested in other arrangements and that the scope of the
invention is not limited to the embodiments described or
illustrated. The scope of the invention is intended only to be
limited by the scope of the claims that follow.
[0018] Referring now to FIG. 1, a line diagram for a conventional
Claus Sulfur Recovery Plant is generally indicated by the numeral
10. Claus Plants have been in use for more than a century at
petroleum refineries to remove sulfur from gases containing
H.sub.2S. Undertaking a brief explanation of a conventional Claus
Plant, referring to Claus Sulfur Recovery Plant 10, gas having
sulfur, typically in the form of H.sub.2S, enters via conduit 12. A
burner 15 along with reaction furnace 18 are provided to burn and
oxidize at least part of the H.sub.25 to elemental sulfur SO.sub.2
and water wherein the reaction is:
10H.sub.2S+5O2.fwdarw.2H.sub.2S+SO.sub.2+7/2S.sub.2+8H.sub.2O
[0019] These very hot gases and vapors are cooled down in a waste
heat boiler 19 and a first condenser 22 where the elemental sulfur
is condensed and removed at liquid discharge conduit 25. Cooling
water is provided to both the waste heat boiler 19 and to the
condenser 22, as shown at inlet 23 to make steam, as shown at
outlet 24, for use in making electricity or elsewhere in the in the
Claus Sulfur Recovery Plant 10 or in the larger industrial plant
that is not shown. The remaining gases from the first condenser 22
are directed through the gas conduit 28 to reheater 30 where the
gases are reheated and then delivered to a catalytic conversion to
elemental sulfur for converting remaining H.sub.2S and SO.sub.2 to
elemental sulfur. The chemical process is generally described as
follows:
2H.sub.2S+SO.sub.2.fwdarw.3S+2H.sub.2O
[0020] Again, the process gases are cooled in the second sulfur
condenser 32 so that elemental sulfur may be condensed to a liquid
and removed at the second liquid discharge conduit 35. The gases
are conventionally directed by a conduit 38 to further sulfur
recovery steps including catalytic reactor 41 and 51 to recover
liquid sulfur at discharge conduits 45 and 55.
[0021] It should be noted that more thorough descriptions of a
Claus system may be found in many other places and there are
doubtless variations known in the art. This description has been
presented simply to describe the improvement related to degassing
the liquid sulfur acquired by most any Claus system.
[0022] Referring now to FIG. 2, a sulfur degassing vessel 60 is
arranged to receive the liquid sulfur from liquid discharge
conduits 25 and 35 at a lower portion of the vessel 60 or at the
bottom of the vessel 60. Inside the vessel 60 is liquid sulfur with
a contained catalyst 62 held within a contact zone 65 that is
generally above the lower portion of the vessel 60. A degassed
liquid sulfur discharge line 66 is arrange to remove liquid sulfur
above the contact zone such that liquid sulfur entering the vessel
60 must pass completely through the contact zone 65 or at least
through a substantial portion of the contact zone 65. The catalyst
62 may take one of several forms. The first form is a plurality of
high surface area alumina particles (spheres, extrudates, etc.)
constrained to prevent being removed or carried away by sulfur flow
from the vessel 60. A second form is a plurality of similarly
constrained high surface area alumina particles impregnated with
iron oxides. A third form is one or more low surface area alumina
porous ceramic foam supports coated with high surface alumina
particles with or without impregnated iron oxide.
[0023] The catalyst 62 converts H.sub.2S.sub.x to H.sub.2S and
elemental sulfur. Reducing the content of H.sub.2S.sub.x at this
stage of the production of liquid sulfur has been found to
substantially reduce the tendency of stored liquid sulfur to slowly
yield H.sub.2S gas. The productivity of the catalyst 62 is enhanced
by agitation, especially by gas. In the present invention, the
agitation gas used to stir the liquid in the contact zone 65 is
supplied with gas via gas conduit 64. The agitation gas is provided
at sufficient pressure to agitate the liquid in contact zone 65 and
be treated in the Claus Sulfur Recovery Plant 10. Gas for agitation
may be augmented by process gas from either gas conduit 28 or gas
conduit 38 or both via lines 28A and 28B. A metering valve may be
arranged in either of lines 28A and 28B, or both, to control the
amount of process gas that may be injected into gas conduit 64 and
fed to the bottom of the vessel in a sparger 63 to agitate the
liquid and the catalyst 62 to carry produced H.sub.2S back to the
Claus Sulfur Recovery Plant 10. The gas in conduit 64 is provided
at a pressure suitable for agitating the liquid in the contact
zone. However, in an alternative arrangement shown in FIG. 5,
nitrogen, carbon dioxide, steam and other inexpensive inert gases
at elevated pressure may be used to raise the pressure of process
gases in lines 28A or 28B by use of an educator 64B.
[0024] Once the gas has passed through the vessel 60, it exits at
exit conduit 68 and rejoins the Claus process downstream of the
source of the process gas at conduit 28. In the preferred
arrangement, the process gas rejoins the Claus process at conduit
48 via conduit 48A. It should be noted that the process gas may
optionally be arranged to rejoin the Claus process at conduit 38 as
shown by dotted line 38A. However, there is a more significant
pressure drop between conduits 28 and 48 to allow for more vigorous
stirring of the catalyst 62 by the process gas from sparger 63. For
even more vigorous stirring, the process gas may optionally be
arranged to rejoin the Claus process further along the system such
as at conduit 51A. This arrangement is shown by dotted line 48B and
may be preferred if the source of the process gas used in vessel 60
comes from conduit 38 via conduit 28B. While the process gas from
the vessel 60 will not have been subjected to all of the successive
treatments in the catalytic reactors 31, 41 and 51, it may have
some vaporous elemental sulfur that could be condensed in condenser
52 and may be subjected to further sulfur removal treatment in a
tail gas unit, which are conventional in Claus plants.
[0025] One additional side reaction occurring in the contact zone
65 worth mentioning is additional conversion of H.sub.2S to
elemental sulfur. The process gas includes some SO.sub.2 and may
reaction on the surface of the catalyst with H.sub.2S that may be
condensed in the liquid sulfur, emanating from the liquid sulfur by
the decomposition of H.sub.2S.sub.x, or contained in the process
gas. This reaction is the same chemical reaction occurring in the
Claus process and is generally described as: 2H.sub.2S+SO.sub.23/x
S.sub.x+2H.sub.2O. Having additional active catalyst for this
chemical reaction to occur yields more liquid sulfur separated from
the industrial process and less sulfur compounds in process
gas.
[0026] It is noted that the agitation gas includes enough H.sub.2S
to warrant sulfur recovery steps so that H.sub.2S recovered in the
vessel 60 is simply and efficiently disposed.
[0027] The process gas, as noted above generally includes H2S.
Process gases in line 28 may contain about 4% to about 9% by volume
H.sub.2S and typically about 8% by volume H.sub.2S. Process gases
in line 38 typically comprise less H.sub.2S, but certainly have
sufficient pressure to agitate the catalyst 62 and return to the
Claus process 10. Process gases in line 38 may have between 2% to
5% H.sub.2S by volume and typically about 4% by volume H.sub.2S.
Process gases in line 48 still retain sufficient pressure to be
used to agitate the catalyst 62 and has a lower H.sub.2S content
being about 0.5% H.sub.2S to about 3% H.sub.2S by volume and
typically about 1% H.sub.2S to about 2% H.sub.2S by volume.
[0028] The full Claus process with the vessel 60 is generally shown
in FIG. 3 showing the side stream of process gas being taken from
line 28 and being carried through the vessel 60 and back into the
Claus process at line 38.
[0029] The vessel 60 may optionally be arranged to receive liquid
sulfur discharged through drains 45 and 55 for degassing. In the
preferred arrangement, the liquid sulfur discharge lines 45 and 55
are combined with the degassed liquid sulfur in line 66. It has
been found that such small streams of liquid sulfur really do not
contain much H.sub.2S.sub.x that needs degassing. Most of the
liquid sulfur is gathered from the first two condensers 22 and
32.
[0030] In an alternative embodiment shown in FIG. 4, the liquid
sulfur may be received at the top of the vessel 60 and liquid
elemental sulfur having the sulfanes removed may be withdrawn at
the bottom of the vessel 60. In this embodiment, the sulfur is
travelling counter to the flow of the process gas through the
reaction zone 65. In FIG. 2, the catalyst zone 65 is shown as being
liquid continuous, whereas, in the alternative embodiment shown in
FIG. 4, the catalyst zone may be gas continuous with the liquid
sulfur trickling down through the contact zone 65.
[0031] Although the systems and processes described herein have
been described in detail, it should be understood that various
changes, substitutions, and alterations can be made without
departing from the spirit and scope of the invention as defined by
the following claims. Those skilled in the art may be able to study
the preferred embodiments and identify other ways to practice the
invention that are not exactly as described herein. It is the
intent of the inventors that variations and equivalents of the
invention are within the scope of the claims while the description,
abstract and drawings are not to be used to limit the scope of the
invention. The invention is specifically intended to be as broad as
the claims below and their equivalents.
* * * * *